A technique using a lever, which clamps a cutting insert to a shank, is well known in the art. According to the International Organization for Standardization (ISO), the cutting insert may be expressed by alphabetic characters, which are predetermined in accordance with a planar shape of the cutting insert. For example, a cutting insert of an equilateral triangle is referred to as a T-type cutting insert, a cutting insert of a square is referred to as an S-type cutting insert, and a cutting insert having an included angle of 35 degrees is referred to as a V-type cutting insert.
FIG. 1 is shows a conventional T-type cutting insert and a T-type lever therefor, as well as a conventional V-type cutting insert and a V-type lever therefor. Referring to FIG. 1, the T-type lever 10T clamps the T-type cutting insert 20T to a shank, while the V-type lever 10V clamps the V-type cutting insert 20V to the shank. The T-type and V-type levers 10T, 10V have extension portions 11T, 11V extending parallel to the cutting insert. Since a length of the V-type cutting insert 20V is longer than a length of the T-type cutting insert 20T, the extension portion 11V of the V-type lever 10V is formed longer than the extension portion 11T of the T-type lever 10T. However, the longer extension portion 11V weakens the strength of the extension portion 11V under the same clamping force. Thus, the V-type lever 10V may be bent or broken by a clamping force required during a cutting operation. This may result in a weakened clamping force of the V-type lever 10V with respect to the V-type cutting insert 20V. There is a demand for developing a cutting tool assembly that resolves such problems and allows for fast and secure clamping of the V-type cutting insert by the lever.